Saturday, July 14, 2018

freezer 2

INDEX to the series

A new small chest freezer was delivered here and put into service yesterday.

Impressively quiet and efficient, my new Danby freezer might be half the weight of the old 1994 Wood freezer that it replaces although they are both the same capacity.

One large delivery guy carried the new boxed freezer from the truck on his shoulder and then slid it gently down the stairs by himself! It then took him and another with a dolly to haul the old Woods away.

Both new and old are the same capacity 7 cubic foot chest freezers separated in time by 25 years.

My freezer is plugged in through an Itead Sonoff S31 which gives me this kWh/day chart through my wifi and control of the outlet in various ways. The kWh/day chart is for June, the last full month of the Woods freezer so we'll have data to compare.

I had updated the Itead app for both iPhone and Android this morning and there are a couple of curiosities. I was surprised to see a degree symbol where I'm pretty sure it means kWh. I had installed the S31 at the freezer outlet on the last day of May so the 0.31 for May is only part of one day. I have not loaded a cost per kWh in the Itead app ewelink since I only need the kWh but the app could calculate the total cost.

So for June I used 26.85 kWh in total for my old freezer, about 0.9 kWh per day. Considering that my whole house used about 8 kWh per day in June, the old freezer was 11% of my usage. My "much newer used" 18 cubic foot refrigerator uses about 0.6 kWh per day. I monitor/control my refrigerator on another S31.

The peakiness of the bars is interesting. Each pair of taller bars shows a weekend when I let the freezer run all day since there is no Time of Use peak priced power on the weekends or holidays. For regular Monday to Friday I use the timer of the S31 to keep the freezer OFF during the peak periods. Currently my utility's peak period is 11am to 5pm so my freezer is OFF for 6 hours when electricity cost here is twice the non-peak rate.

I don't buy peak priced electricity for my freezer and I use less electricity, saving about 10-12% on each day I inhibit operation during the peak period. The freezer has to "catch up" for the time it has been off, but it does not use as much as if it had been ON the whole time.

I can also see that the freezer uses less electricity on Mondays! I guess it catches up on the weekend cheap power so takes a bit of a break?

One thing about my freezer and possibly most freezers is that I don't open the door very often, maybe once every couple of days. If the door got opened often and items loaded or removed, the kWh usage would be more scattered, less regular.

So what happens to the temperature in the freezer when the power is turned off for six hours? I knew you were going to ask.

[click pics to enlarge]

This is the temperature inside the Woods freezer last August one hot day. I am using an Elitech RC4 Temperature Data Logger. By the end of 6 hours the air in the top of the freezer has warmed but no higher than -4C. I am surprised that it did so well given the age and condition of the seals.

I am confident that the new Danby will do much better!

Thanks for your interest.

George Plhak
Lions Head, Ontario, Canada

PS - Here is the EnerGuide label for my new freezer (Canada version). We will measure how well it does here.

Update July 21 - I changed the freezer July 13. Here is the daily usage reported by the outlet which runs the freezer. The vertical axis is kWh/day, the horizontal is the day of the month. It looks like the usage will be reduced by half with the new freezer!

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